Agardite
Agardite is a mineral group consisting of agardite-, agardite-, agardite-, and agardite-. They comprise a group of minerals that are hydrous hydrated arsenates of rare-earth elements and copper, with the general chemical formula Cu636·3H2O. Yttrium, cerium, neodymium, lanthanum, as well as trace to minor amounts of other REEs, are present in their structure. Agardite- is probably the most often found representative. They form needle-like yellow-green crystals in the hexagonal crystal system. Agardite minerals are a member of the mixite structure group, which has the general chemical formula Cu2+6A36·3H2O, where A is a REE, Al, Ca, Pb, or Bi, and T is P or As. In addition to the four agardite minerals, the other members of the mixite mineral group are calciopetersite, goudeyite, mixite, petersite-, petersite-, plumboagardite, and zálesíite.
Agardite- from the Bou Skour mine in Djebel Sarhro, Morocco was the first of the agardite-group minerals to be characterized. It was described by Dietrich in 1969 and was named after Jules Agard, a French geologist at the Bureau de Recherches Géologiques et Minières, Orléans, France. Agardite-group minerals have subsequently been found in Germany, Czech Republic, Greece, Italy, Japan, Namibia, Poland, Spain, Switzerland, the United Kingdom, and the United States.
